1. Field of the Invention
The present invention relates to a developing apparatus for developing a presensitized plate and, more particularly, it relates to a developing apparatus in which unevenness is not generated during development.
2. Description of the Prior Art
A developing apparatus of particular interest to the present invention is disclosed in Japanese Utility Model Laying-Open No. 34154/1986 entitled "A Cooling Apparatus for a Copying Machine" which is assigned to the applicant of the present invention. FIG. 1 shows a conventional developing apparatus. The developing apparatus is contained within a copying machine 30.
The presensitized plate to be developed comprises a plastic film base and an emulsion layer formed thereon. The emulsion layer comprises a silver halide photosensitive surface such as silver halide emulsion. After development and fixation, the presensitized plate is used as an offset printing plate.
Referring to FIG. 1, a conventional developing apparatus comprises a developer tank 33 for storing a developer 32, a feed roller 36 provided on the side of a presensitized plate inlet 34 of the developer tank 33 for feeding the presensitized plate 35 into the developer 32, a discharging roller 38 provided on the side of a presensitized plate outlet 37 of the developer tank 33 for discharging the presensitized plate 35 into a stabilizing unit 42, and a guide member 41 provided in the developer tank 33 for guiding the fed presensitized plate 35 to the discharging roller 38. The guide member 41 comprises a conveyer path 40 for guiding the presensitized plate 35.
The exposed presensitized plate 35 is fed through the presensitized plate inlet 34 and the feed roller 36 along the conveyer path provided in the developer tank 33 while immersed in the developer. The immersed presensitized plate 35 is fed through the discharging roller 38 into the stabilizing unit 42 for the succeeding step of the process.
FIG. 2 is an enlarged view showing the feed roller 36. Referring to FIG. 2, the feed roller 36 comprises a pair of pinch rollers 36a and 36b and an auxiliary roller 36c provided thereunder.
The presensitized plate 35 which is fed by the pinch rollers 36a and 36b is introduced into the developer 32 via the auxiliary roller 36c. Since the above described developing apparatus has relatively a simple structure, it is often used within copying machines and the like.
However, recently the sensitivity of presensitized plates has been improved. Since the sensitivity in development has been enhanced, the development of the presensitized plate 35 becomes uneven if there are even small ripples in the developer. The above described conventional developing apparatus, presents the following problems: Referring to FIG. 1, when the presensitized plate 35 is discharged from the developer tank 33, the edge of the plate 35 runs against the discharging roller 38. When this happens, the feeding of the presensitized plate 35 is momentarily stopped. However, at the other side of the developer tank 33, the presensitized plate 35 is still being fed. Consequently, the presensitized plate 35 is bent. This situation is shown in phantom in FIG. 2 in an exaggerated manner. As shown, the presensitized plate 35 is forced back in the direction of the arrow A. Therefore, ripples are formed on the surface of the liquid S near the introducing side of the developer tank 33. The ripples cause unevenness in development. The same situation occurs when the rear edge of the presensitized plate 35 passes the feed roller 36.